Perhaps not, but it seems that the fall of any form of government is preceded by widespread corruption of everyone from the most elite to the lowest peasant.
A society can handle a few leaches, but when everyone is a leach the end is near.
It’s the same old story repeated over and over from the beginning of civilization.
Tacitus was pretty insightful so I wouldn’t be surprised if he thought the empire would eventually collapse.
It is possible, but saying anything like that publicly would have been bad for his health.